The study will continue on the biosynthesis of retinal-C14 (or H3) and retinal-C14 (or H3) from acetate - C14 and Beta-carotene-H3 in the corpus luteum. The effects of retinal, retinol and retinoic acid on the metabolism of pregnenolone to progesterone, and progesterone to pregnenolone will be investigated further. Also included will be a study of the effects of a vitamin A deficient diet on the Beta-hydroxysteroid dehydrogenase activity in rat ovaries.